Opel Corsa B 1993–2000 Service and Repair Manual: Vacuum servo unit - testing, removal and refitting

Testing

1. To establish whether or not the servo is operating, proceed as follows.

2. With the engine not running, apply the brake pedal several times to exhaust any residual vacuum.

3. Hold the brake pedal depressed and start the engine. The pedal should be felt to move down when the engine starts. If not, check the vacuum hose and non-return valve.

4. If the vacuum system is satisfactory, the servo itself is faulty and must be renewed.

Removal

Right-hand drive

5. Remove the vacuum connector from the servo.

6. Remove the nuts which secure the master cylinder to the servo and draw the cylinder away from the servo. There is no need to disconnect the hydraulic pipes, but be careful not to strain them.

7. Inside the car, remove the stop-lamp switch and disconnect the brake pedal clevis .

8. The servo must now be removed from its bracket. The recommended method is to undo the two 6 mm Allen screws which hold the bracket halves together. Access to these screws is obtained by removing the wiper arms, wind deflector and water deflector; the screws are then accessible through two holes which may have rubber plugs in them. The screws are extremely tight, and without doubt a well-fitting key and square drive adapter will be needed (see illustration).

Removing a servo bracket screw

9. If the Allen screws cannot be undone, it is possible to reach behind the servo and undo the four nuts which hold it to the bracket (see illustration). Small hands, some dexterity and a good deal of patience will be needed. The nuts are of the self-locking type and resist removal all the way.

Three of the four servo-to-bracket nuts (arrowed) servo and bracket removed for clarity

10. With the screws or nuts removed, the servo can be removed from the car.

Left-hand drive

11. The procedure is similar to that just described, but access to the servo bracket fastenings is much easier. If power steering is fitted, a flexible head socket drive will be needed to reach the lower nut without disturbing the steering gear (see illustrations). On all models it will be necessary to remove the windscreen washer reservoir.

Three servo mounting nuts (arrowed) - Left-hand drive models

Servo mounting nut (arrowed) obscured by steering gear - Left-hand drive models

Refitting

12. If a new servo is to be fitted, transfer the clevis and locknut to it. On right-hand drive models, measure the fitted position of the clevis on the old servo pushrod and fit it in the same position on the new one. On left-hand drive models, when transferring the clevis and threaded sleeve to the new servo, set the clevis-to-servo distance as shown (see illustration).

Servo clevis adjustment - Left-hand drive models

A = 278.5 mm (10.97 in)

1. Use sealing compound on the bracket halves if they were separated (see illustration).
2. Make sure the vacuum connection point is in the correct position (see illustration).
3. Use thread locking compound or new self-locking nuts, as appropriate.

13. The remainder of refitting is a reverse of removal, noting the following points:

Servo mounting bracket lower half remains on bulkhead

Fit the servo with the vacuum connector (arrowed) positioned as shown